1. Field of the Invention
The present invention generally relates to an improved process for fully distributing gas bubbles throughout a liquid body in order to accomplish solid-liquid or liquid-liquid separation by flotation.
2. State of the Art
Gas flotation techniques are commonly used for separating and concentrating valuable minerals and chemicals, for removing contaminating particulates from liquid bodies and for separating various liquids (e.g., oil and water). For example, a typical flotation process in the mineral beneficiation art includes the steps of conditioning an aqueous pulp or slurry of crushed ore with a chemical flotation aid and then dispersing air bubbles within the pulp to produce a surface froth relatively rich in the desired mineral. In the field of oil production, similar flotation processes are frequently used to separate crude oil from water prior to the reinjection of the water into a well or prior to surface disposal of the water. In all flotation processes it is important to maximize contact between the froth-producing gas bubbles and the materials which are to be floated. Therefore, it is important that the gas bubbles be distributed throughout the liquid body. Another requirement is that the surface of the liquid body be maintained fairly quiescent so that the froth is not agitated to cause the floated materials to separate from the gas bubbles to which they have become attached.
Various processes have been proposed to satisfy the afore-mentioned requirements. In one well-known type of machine, a rotatable impeller aspirates gas into a liquid body in a vessel and, at the same time, agitates the liquid to distribute the gas within the vessel. An example of that type of machine is shown in U.S. Pat. No. 3,491,880 to W. H. Reck. In another type of flotation machine it has been proposed to use one or more gas injection nozzles in combination with a baffle arrangement to accomplish gas distribution within a liquid body. Machines generally of that type are shown in U.S. Pat. Nos. 2,008,624; 3,371,779; and 3,446,353.
Another type of flotation machine for mineral applications is the cascade machine; cascade machines, which were historically of quite small cell volume, have been obsolete for many years. Examples of cascade machines are shown in U.S. Pat. No. 1,380,665 to F. J. Lyster and U.S. Pat. No. 1,311,919 to Seale and Shellshear.